If You Have This, Your Pfizer or Moderna Vaccine Is Less Effective, Study Finds

New research has pinpointed a common condition that may lower your vaccine response.

The Pfizer and Moderna COVID shots have been pivotal vaccines in the U.S.' race to end the pandemic. More than 85 million people in the country have been fully vaccinated with Pfizer and 62 million with Moderna, according to the latest data from the Centers for Disease Control and Prevention (CDC). Nevertheless, a small number of these fully vaccinated individuals are still getting infected with COVID, as a number of factors—like the rapidly spreading Delta variant—may diminish the efficacy of both vaccines. Now, research has found one common condition that can also lessen your vaccine protection if you received either of these shots.

RELATED: If You Got Pfizer or Moderna, the FDA Says Watch for These Delayed Side Effects.

The study, which was published July 13 in JAMA Internal Medicine, sought to find out how much protection the two approved mRNA vaccines give people with cirrhosis. Cirrhosis is severe scarring of the liver that can be caused by many forms of liver disease and other conditions like hepatitis and chronic alcoholism, per the Mayo Clinic.

Researchers for the study analyzed more than 20,000 people with cirrhosis who received at lease one dose of either Pfizer or Moderna and compared their experience to more than 20,000 cirrhosis patients who were not vaccinated. According to the study, one dose of an mRNA vaccine is only 64.8 percent effective against COVID infection and two doses is 78.6 percent effective against infection.

The CDC reports that the Pfizer vaccine is generally 95 percent effective against infection after two doses based on evidence from clinical trials. Moderna, on the other hand, is 94.1 percent effective after two doses in the general population based on evidence from clinical trials. That means these vaccines are slightly less protective in people with cirrhosis, the study concludes.

But effectiveness against hospitalization or death was still high for cirrhosis patients. According to the study, both one and two doses of an mRNA vaccine were associated with a 100 percent reduction in COVID hospitalization and death for cirrhosis patients. No one in the vaccinated group died from COVID, but there were two COVID deaths in the unvaccinated cirrhosis group.

"Patients with cirrhosis who are vaccinated might still get the infection, but they are unlikely to die or get hospitalized with COVID-19," lead study author Binu V. John, MD, an affiliate associate professor at the University of Miami Miller School of Medicine, confirmed in a statement.

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Having cirrhosis is also likely to delay your vaccine response. According to the study, there was no notable difference between the vaccinated and unvaccinated cirrhosis groups the first 28 days after the first dose. It was only after those 28 days that the 64.8 percent efficacy against infection and 100 percent efficacy against hospitalization or death kicked in.

"The difference starts to kick in after 28 days. That's when you start to see fewer cases in the vaccine group and more in the unvaccinated group," John said. He added that clinicians who work with cirrhosis patients may want to caution them about their delayed immune protection.

RELATED: If You Take These Meds, You May Not Have Antibodies Post-Vaccine, Study Says.

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